Adiabatic elastic constants of a composite composed of 25 volume percent of silicon carbide (SiC) whiskers in 2014 aluminum matrix are measured to 1.5 GN/m2. Whereas the pressure derivative of bulk modulus of the composite exceeds those of its two constituents, the pressure derivative of the shear modulus of the composite lie between those of its constituents. Calculated values of the upper and lower bounds of these moduli of the composite appear to be insensitive to the pressure derivative of the shear modulus of SiC. A new modified and simple model of such a composite predicts the values of the elastic constants of this composite fairly well at both the ambient pressure and 1.5 GN/m2.